1. Field of the Invention
The present invention relates to lamp flashers and more particularly to apparatus for flashing lamps in particular code sequences and for synchronizing a number of lamp flashing systems.
2. Background of the Invention
Marine buoys and beacons commonly use incandescent lamps which are periodically flashed in various sequences of short and long flashes separated by short and long eclipses for identification of channels, obstructions and other navigational features. Many such devices are battery operated and conservation of primary power is important. In recent years, older flashing systems using motors and relays have been supplanted by transistor timing and control circuits. For example, see the following U.S. patents to Seidler: U.S. Pat. Nos. 3,244,892; 3,310,708; and 3,596,113. To obtain reliability and accurately timed signals, voltages must be regulated. To eliminate relays, transistor switches have been used. Prior art regulating and switching transistors have generally been germanium types to minimize voltage drops; however, these types have high leakage, especially at high temperatures. Lower leakage at high temperatures can be obtained with the use of silicon transistors but at the expense of higher voltage drops.
In many applications, a number of beacons or buoys are required to operate in synchronism, and generally, a master flasher controls a set of slave units. When the master fails, improper operation of the slaves is common. A need exists for a flexible easily programmable flasher control circuit that will minimize primary power drain, that will permit any unit to synchronize the remaining units, that will not fail when other units fail, and which will permit almost any coded signals to be generated.